Changes in bone due to age and disease, manifested as a change in mineral content and collagen structure, is associated with loss of mechanical properties and can be detected by ultrasonics and other physico-chemical tests. Past efforts have shown the structure to be more complex than envisioned. An improved model of the mineral structure is being developed. Insight and understanding is sought for the elastic properties at the ultrastructural level using the new powerful instrumentation like the Atomic Force Microscope, the Ultrasonic Microscope and Backscattered Electron Microscope. The availability of digitized images from these instruments reduces the labor needed to relate the density and elastic constants of the ultrastructural bone elements (mineralized fibrils and fibers). An adequate data base will be generated to test models of the mineralized tissue. Advice given to patients suffering from various bone diseases is often contradictory. One year osteoporosis is treated with calcium and the next year it is regarded as useless. There is a need for a well substantiated theory of the mineralization process to provide a rational basis for treatment of osteoporosis, Paget's disease and other bone diseases. It is necessary to know the structure of the basic elements of mineralized tissue to understand how tissue mineralizes and how to influence the process. Previous work in this program has provided considerable insight into the structure of mineralized tissue. The proposed work will add substantially to the available body of information.